Action research on electrochemistry learning. Conceptual modelling intervention to promote disciplinary understanding, scientific inquiry, and reasoning

Students in engineering-science programmes often struggle with theoretical concepts, while they tend to adopt a surface approach to learning. We suggest that this can be tackled by promoting a specific higher-order thinking skill (HOTS) that enables drawing connections between physical phenomena and theoretical concepts representing them. We designed an intervention to support students in achieving deep insight into electrochemical phenomena, while developing this HOTS. Such intervention aims to scaffold students’ learning and development by introducing conceptual modelling as an essential thinking skill of engineering-scientists, and as a strategy to build scientific understanding of natural phenomena. Therefore, conceptual modelling constitutes a main learning objective of this novel course. This paper reports an empirical investigation into how students deal with concepts and complexity, and to what extent the intervention has any measurable effects on the learning outcomes. This phenomenological investigation integrates considerations from various disciplines, and relies on multiple data sources, i.e., students’ documents (lab journals and reports), observations of students in action (in discussions with their tutors and while performing lab experiments), and video stimulated-recall interviews. The results show little effect of the intervention, as implemented, suggesting how challenging it is for students (and instructors) to shift from traditional learning-and-teaching approaches, towards an epistemology of knowledge construction for specific problems. The findings are informative for revision of the intervention and generate specific recommendations. Concurrently, our operationalisation of the conceptual framework proves powerful in detecting qualitative differences in HOTS. Plausible implications for research and educational practice in science-engineering education are discussed

Action research on electrochemistry learning. Conceptual modelling intervention to promote disciplinary understanding, scientific inquiry, and reasoning

Students in engineering-science programmes often struggle with theoretical concepts, while they tend to adopt a surface approach to learning. We suggest that this can be tackled by promoting a specific higher-order thinking skill (HOTS) that enables drawing connections between physical phenomena and theoretical concepts representing them. We designed an intervention to support students in achieving deep insight into electrochemical phenomena, while developing this HOTS. Such intervention aims to scaffold students' learning and development by introducing conceptual modelling as an essential thinking skill of engineering-scientists, and as a strategy to build scientific understanding of natural phenomena. Therefore, conceptual modelling constitutes a main learning objective of this novel course. This paper reports an empirical investigation into how students deal with concepts and complexity, and to what extent the intervention has any measurable effects on the learning outcomes. This phenomenological investigation integrates considerations from various disciplines, and relies on multiple data sources, i.e., students' documents (lab journals and reports), observations of students in action (in discussions with their tutors and while performing lab experiments), and video stimulated-recall interviews. The results show little effect of the intervention, as implemented, suggesting how challenging it is for students (and instructors) to shift from traditional learning-and-teaching approaches, towards an epistemology of knowledge construction for specific problems. The findings are informative for revision of the intervention and generate specific recommendations. Concurrently, our operationalisation of the conceptual framework proves powerful in detecting qualitative differences in HOTS. Plausible implications for research and educational practice in science-engineering education are discussed.</p

Building micro-soccer-balls with evaporating colloidal fakir drops

Evaporation-driven particle self-assembly can be used to generate three-dimensional microstructures. We present a new method to create these colloidal microstructures, in which we can control the amount of particles and their packing fraction. To this end, we evaporate colloidal dispersion droplets on a special type of superhydrophobic micro-structured surface, on which the droplet re- mains in Cassie-Baxter state during the entire evaporative process. The remainders of the droplet consist of a massive spherical cluster of the microspheres, with diameters ranging from a few tens up to several hundreds of microns. We present scaling arguments to show how the final particle packing fraction of these balls depends on the dynamics of the droplet evaporation.Comment: Manuscript Submitted to Physical Review Letters, 29th February 201

Exploring the mechanical properties of additively manufactured carbon-rich zirconia 3D microarchitectures

Two-photon lithography (TPL) is a promising technique for manufacturing ceramic microstructures with nanoscale resolution. The process relies on tailor-made precursor resins rich in metal-organic and organic constituents, which can lead to carbon-based residues incorporated within the ceramic microstructures. While these are generally considered unwanted impurities, our study reveals that the presence of carbon-rich residues in the form of graphitic and disordered carbon in tetragonal (t-) ZrO2 can benefit the mechanical strength of TPL microstructures. In order to achieve a better understanding of these effects, we deconvolute the structural and materials contributions to the strength of the 3D microarchitectures by comparing them to plain micropillars. We vary the organic content by different thermal treatments, resulting in different crystal structures. The highest compression strength of 3.73 ± 0.21 GPa and ductility are reached for the t-ZrO2 micropillars, which also contain the highest carbon content. This paradoxical finding opens up new perspectives and will foster the development of “brick and mortar”-like ceramic microarchitectures

One-step sculpting of silicon microstructures from pillars to needles for water and oil repelling surfaces

Surfaces that repel both water and oil effectively (contact angles > 150°) are rare. Here we detail the microfabrication method of silicon surfaces with such properties. The method is based on careful tuning of the process conditions in a reactive etching protocol. We investigate the influence of SF6, O2 and CHF3 gases during the etching process using the same pitch of a photolithographic mask. Varying the loading conditions during etching, we optimized the conditions to fabricate homogeneous pedestal-like structures. The roughness of the microstructures could also effectively be controlled by tuning the dry plasma etching conditions. The wetting behavior of the resulting microstructures was evaluated in terms of the water and oil contact angles. Excitingly, the surfaces can be engineered from superhydrophobic to omniphobic by variation of the aforementioned predefined parameter

Additive manufacturing of 3D yttria-stabilized zirconia microarchitectures

The additive manufacturing (AM) of yttria-stabilized zirconia (YSZ) microarchitectures with sub-micrometer precision via two-photon lithography (TPL), utilizing custom photoresin containing zirconium and yttrium monomers is investigated. YSZ 3D microarchitectures can be formed at low temperatures (600 °C). The low-temperature phase stabilization of ZrO2 doped with Y2O3 demonstrates that doping ZrO2 with ≈ 10 mol% Y2O3 stabilizes the c-ZrO2 phase. The approach does not utilize YSZ particles as additives. Instead, the crystallization of the YSZ phase is initiated after printing, i.e., during thermal processing in the air at 600 °C – 1200 °C for one and two hours. The YSZ microarchitectures are characterized in detail. This includes understanding the role of defect chemistry, which has been overlooked in TPL-enabled micro-ceramics. Upon UV excitation, defect-related yellowish-green emission is observed from YSZ microarchitectures associated with intrinsic and extrinsic centers, correlated with the charge compensation due to Y3+ doping. The mechanical properties of the microarchitectures are assessed with manufactured micropillars. Micropillar compression yields the intrinsic mechanical strength of YSZ. The highest strength is observed for micropillars annealed at 600 °C, and this characteristic decreased with an increase in the annealing temperature. The deformation behavior gradually changes from ductile to brittle-like, correlating with the Hall–Petch strengthening mechanism.</p